The big picture: Anti-TPO antibodies are produced by the immune system when it mistakenly targets thyroid peroxidase (TPO), an enzyme crucial for thyroid hormone production. High levels of anti-TPO antibodies suggest that the immune system is attacking the thyroid, which can lead to autoimmune thyroid diseases like Hashimoto’s thyroiditis or Graves’ disease.

Role in thyroid function: TPO is essential for the synthesis of thyroid hormones. It helps the thyroid gland convert iodine into thyroxine (T4) and triiodothyronine (T3), which regulate metabolism, energy levels, and numerous bodily functions. When Anti-TPO antibodies are present, they disrupt the normal function of TPO, impairing hormone production and leading to inflammation and, over time, possible destruction of thyroid tissue.

Autoimmune thyroid disease: Anti-TPO antibodies are most commonly associated with autoimmune thyroid conditions, including:

Hashimoto’s thyroiditis: The most common cause of hypothyroidism, where the immune system attacks the thyroid, leading to chronic inflammation and gradual loss of thyroid function. Elevated anti-TPO levels are seen in about 90% of individuals with Hashimoto’s.
Graves’ disease: An autoimmune disorder that causes hyperthyroidism due to overactive thyroid function. Anti-TPO antibodies may be present in some cases, although other antibodies, such as TSH receptor antibodies, are more specific to Graves’ disease.

High Anti-TPO levels: Elevated anti-TPO levels suggest ongoing autoimmune activity against the thyroid. While high levels may not immediately cause symptoms, they often precede the development of thyroid dysfunction. In hypothyroidism (such as in Hashimoto’s), high anti-TPO indicates progressive thyroid damage, potentially leading to symptoms like fatigue, weight gain, cold intolerance, dry skin, and depression. In hyperthyroidism (such as in Graves’ disease), symptoms may include weight loss, anxiety, tremors, heat intolerance, rapid heart rate, and insomnia.

Low or absent anti-TPO levels: A low or absent level of anti-TPO antibodies is typically seen in individuals without autoimmune thyroid disease. However, it’s still possible to have thyroid dysfunction without elevated anti-TPO antibodies, so other thyroid tests, such as TSH, free T4, and free T3, are needed to assess overall thyroid function.

Managing high Anti-TPO levels: In cases of hypothyroidism (like Hashimoto’s), thyroid hormone replacement therapy (e.g., levothyroxine) can help restore normal thyroid function. Addressing inflammation through diet (e.g., anti-inflammatory or autoimmune protocols), managing stress, and optimizing nutrient intake (such as selenium and vitamin D) may support thyroid health and reduce the progression of autoimmune thyroid disease.